I am learning to work with procedural surfaces in my AutoCAD 2012 Surface Modeling chapter. I just created an arc surface on the ground plane (using world UCS) The book is then wanting me to create a circle on the plane Y = 0. I know this is a very simple thing to do but i am new to the AutoCAD 2015 program. The book gave a hint : Rotate the UCS so that the Y = 0 plane becomes the ground plane, use the ViewCube to change the view to show the two surfaces, create the circle, then return to the World UCS. I have tried rotating the UCS so that y = 0. Can somebody please help me with this simple step? I would greatly appreciate it! Thanks